DE102018107220A1 - Method for calculating a quantity of soot in a particle filter - Google Patents

Abstract

The invention relates to a method according to the invention for calculating a quantity of soot Ms in a particulate filter (2) which, in the calculation, takes into account a soot reduction Min of the particulate filter (2). For the soot reduction calculation, a first particulate filter temperature T and an oxygen amount Mo are considered.

Description

The invention relates to a method for calculating a soot amount Ms in a particulate filter, an exhaust aftertreatment system and a computer program product.

The DE102014006692A1 discloses a gasoline engine with particulate filter and regeneration strategy and method thereto.

The method according to the invention for calculating a soot quantity Ms in a particulate filter takes into account a soot reduction M _SR in the particulate filter during the calculation, and takes into account a first particulate filter temperature T ₁ and an oxygen quantity Mo in the calculation of the soot reduction M _SR.

The purpose of the particulate filter is to filter soot from an exhaust gas stream. The exhaust gas flow is generated by combustion, for example by combustion in a combustion chamber of an internal combustion engine. The soot comprises particles which are produced as a by-product during combustion. The soot remains in the particulate filter, which increases the amount of soot Ms, which is located in the particulate filter. The thus-filtered soot is thereby not covered by an exhaust gas flow downstream of the particulate filter.

The filter effect of the particulate filter is dependent on the amount of soot Ms, which is located in the particulate filter. For a larger amount of soot Ms in the particulate filter increases the filter effect of the particulate filter. For the operation of the internal combustion engine, in particular for compliance with legal regulations on exhaust gas purity, it is therefore advantageous to determine the amount of soot Ms and, based thereon, the filtering effect of the particulate filter and / or to calculate.

When calculating the amount of soot Ms in the particulate filter, the soot reduction M _{SR is} taken into account subtractive. A calculation of the soot reduction M _SR is therefore relevant for a determination of the amount of soot Ms.

For example, during longer coasting phases during operation of the internal combustion engine, there is an increased amount of oxygen Mo in the particulate filter. Depending on the particulate filter temperature T ₁ , the soot burn-off causes soot reduction M _SR in the particulate filter. The soot reduction M _SR is the amount of soot that is no longer in the particulate filter due to combustion of the soot. Higher temperatures T ₁ lead to an increase in the rate of burnup. The rate of burnup is higher, for a faster soot reduction M _SR . The reason for this is that an increase of the temperature T ₁ leads to an acceleration of chemical reactions, which lead to the burnup of the soot. The temperature T ₁ describes the temperature of the particulate filter, which has this at the beginning of the burnup.

Based on the amount of oxygen Mo, which is available for the soot reduction M _SR , there is an increase in the rate of burnup for increasing the amount of oxygen Mo up to a limit for the amount of oxygen. For an oxygen amount Mo exceeding the limit value for the amount of oxygen, the rate of burnup remains approximately constant. The reason for this is that from the limit for the amount of oxygen enough oxygen for the reaction and thus the combustion of the soot is available. An additional presence of oxygen therefore does not result in an increase in the rate of burnup.

The consideration of T ₁ and M _O for the soot reduction M _SR allows a more accurate calculation of the amount of soot Ms in the particulate filter, and thus a more accurate calculation of the filter effect. A more accurate calculation in this case means that the results of the calculations for the soot amount Ms match better with an actual soot amount that is in the particulate filter. This allows a more environmentally friendly operation of the internal combustion engine, since internal combustion engine parameters, for example, for the metering of a fuel for combustion, can be set optimized for the actual filtering effect. The actual filter effect is the filter effect of the particulate filter, which results from the actual amount of soot that is in the particulate filter.

In addition, a temperature T ₂ (M _S1 ) for the calculation of the soot reduction M _{SR is} taken into account for the method. Due to the chemical reactions that occur during the combustion of soot in the particulate filter, the temperature of the particulate filter changes. This change is taken into account in the temperature T ₂ (M _S1 ).

The increase in temperature is based on exothermicity which occurs when the soot burns. This leads to an increase in the rate of burnup. To take account of this increase in the calculation, the temperature of the particulate filter T ₂ (M _S1 ) rising due to exothermicity is taken into account. This also results in a dependence on an existing first soot loading M _S1 . For a higher first soot loading M _S1 results in a higher temperature T ₂ (M _S1 ), since a larger amount of soot is available for the burn-up. The burnup itself has a further increase of the temperature T ₂ (M _S1 ) due to exothermicity. This increases the rate of burnup.

In addition, the temperature T ₂ (M _S1 ) increases with an increasing duration t _SR for the method. The duration t _SR is the duration over which the combustion of the soot takes place. For a longer duration t _SR , the rate of burnup increases up to a duration limit. Thereafter, the rate of burnup decreases again, based on the duration t _SR .

The limit value for the duration is characterized by the soot reduction M _SR . As soon as a portion of the amount of soot Ms is burned, the number of reactants for the following exothermic reaction decreases, whereby the temperature T ₂ (M _S1 ) decreases. This entails a decrease in the rate of burnup.

The additional consideration of the parameters M _S1 , T ₂ (M _S1 ) and t _SR allows a calculation of the amount of soot M _S , which better coincides with the amount of soot actually present in the particulate filter, since physical and chemical processes that take place during the combustion of the soot better be mapped by the calculation. This allows an additional increased accuracy for the calculation of the soot reduction M _SR , and thus the soot amount Ms and the filtering effect of the particulate filter.

In addition, a more accurate determination and / or calculation of the actual filter effect of the particulate filter and thus a more environmentally friendly operation of the internal combustion engine is made possible because engine parameters, for example, for combustion, optimized for the actual filtering effect can be selected.

The exhaust aftertreatment system according to the invention comprises a controller for a particulate filter and a particulate filter, wherein the controller is set up for carrying out a method according to the invention.

The computer program product according to the invention comprises a program which, when executed by a controller according to the invention, causes the controller to carry out a method according to the invention.

The inventive method allows a more accurate calculation of the actual filtering effect of the particulate filter. This makes it possible for the controller according to the invention, for example by the use of the computer program product according to the invention, to control the particulate filter in such a way that statutory regulations on exhaust gas purity are not exceeded. In addition, this allows a more environmentally friendly operation of the engine.

The dependent claims describe further advantageous embodiments of the invention.

Preferred embodiments will be explained in more detail with reference to the following figure.

1 shows an inventive exhaust aftertreatment system 1 comprising a controller 3 for a particle filter 2 and a particle filter 2 , An embodiment of the inventive method for calculating a soot amount Ms in a particulate filter 2 takes into account in calculation a soot reduction M _SR in the particulate filter 2 , wherein in the calculation of the soot reduction M _SR a first particulate filter temperature T ₁ and an oxygen amount Mo are taken into account.

The soot reduction M _SR and thus the burnup and in particular the rate of burnup of soot in a particulate filter 2 are dependent on T ₁ and M _O. This dependence is for example in a first map in the controller 3 deposited.

In a further exemplary embodiment, the method according to the invention takes into account a second particle filter temperature T ₂ (M _S1 ) for the calculation, wherein T ₂ (M _S1 ) is dependent on an existing first soot load M _S1 .

For mere consideration of T ₁ and M _O, it is disregarded that the temperature of the particle filter 2 increased during the burn by exotherm.

This dependency is, for example, in a second characteristic field and / or by a first set of polynomials and / or a first set of value tables in the controller 3 deposited. The second characteristic map and / or the first set of polynomials and / or the first set of value tables are taken into account in a first modulation of the first characteristic field. The first modulation of the first characteristic map makes it possible to specify the first characteristic field with more accurate values.

This allows an additional increased accuracy in the determination and / or calculation of the actual filtering effect of the particulate filter 2 , This allows a more environmentally friendly operation of the internal combustion engine.

In a further exemplary embodiment, the method according to the invention for the calculation of the soot reduction M _SR takes into account a duration t _SR.

The result is a higher rate of burnup for longer durations t _SR of the burnup up to a limit value for the duration of the burnup. Thereafter, the rate of burnup decreases with respect to the duration t _SR . A limit value for the duration t _SR is, for example, a time of approximately 20 s. During this time, most of the soot in the particulate filter 2 burned down. This reduces the amount Carbon black, which is available for the following exothermic reaction, whereby the temperature T ₂ (M _S1 ) decreases. This entails a decrease in the rate of burnup.

The dependence of the rate of erosion of the duration t _SR is, for example, as a second polynomial and / or as a second value table in the controller 3 stored, and is taken into account in a second modulation of the first map. The second modulation of the first characteristic map makes it possible to specify the first characteristic field with more accurate values.

This allows an additional increased accuracy in the determination and / or calculation of the actual filtering effect of the particulate filter 2 , This allows a more environmentally friendly operation of the internal combustion engine.

In a further embodiment, a first action for soot reduction in the particulate filter 2 aborted when the soot reduction M _SR exceeds a threshold for soot reduction.

The first action may be a coasting phase of the internal combustion engine. In the process, the value for Mo increases and at a sufficiently high temperature T1, soot burns off in the particle filter 2 , As the filter effect of the particulate filter 2 depends on the amount of soot Ms, which is in the particulate filter 2 is so a minimum filter effect can be determined for the operation of the particulate filter 2 ,

Based on the calculations for soot amount Ms and soot reduction M _SR in the particulate filter 2 , a minimum amount of soot Ms and / or a maximum soot reduction M _SR can be determined, for which the minimum filtering effect is achieved. When the minimum amount of soot and / or the maximum soot reduction is reached, the overrun phase of the internal combustion engine is terminated. A first abort condition includes this abort.

As a result, a minimum filter effect is ensured, which allows a more environmentally friendly operation of the internal combustion engine.

In a further embodiment, the first action is aborted when the duration t _SR exceeds a limit for the duration. A second abort condition includes this abort.

This second termination condition is an alternative to the first termination condition, and also ensures a minimum filtering effect of the particulate filter 2 , The calculation of the amount of soot Ms is based on the duration t _SR for the burnup. As a result, a maximum duration for the burnup can be determined so that a minimum filter effect is ensured. The second termination condition can be determined faster than the first termination condition, since the exotherm for the burnup is not explicitly taken into account.

Advantageously, this ensures a faster calculation of a minimum filter effect, which allows a more environmentally friendly operation of the internal combustion engine.

In a further exemplary embodiment, the method comprises carrying out a second action for completely burning off the amount of soot Ms in the particle filter 2 ,

After complete combustion of soot from the particle filter 2 This results in an actual amount of soot of zero in the particulate filter 2 , This value can also be used for the calculation of the soot quantity Ms for this point in time at which the complete burnup takes place. This will match the actual amount of soot in the particulate filter 2 and reaches the calculated amount of soot Ms. This allows errors to be reset to the calculation of Ms. Errors can follow from the inaccurate mapping of physical and chemical processes through the calculation. Resetting errors allows a more accurate calculation of Ms.

For example, the second action may also be active by the controller 3 be triggered to reduce errors on the calculation of Ms. The second action may be a coasting phase of the internal combustion engine.

A more accurate calculation of Ms allows a more environmentally friendly operation of the internal combustion engine, as combustion engine parameters, for example, for combustion, optimized for the actual filtering effect can be selected.

The described embodiments may be performed individually or in combination.

The exhaust aftertreatment system according to the invention 1 includes a controller 3 for a particle filter 1 and a particle filter 1 , where the controller 3 is set up for carrying out a method according to the invention.

The computer program product according to the invention comprises a program that, if it is from a controller 3 running, the controller 3 causes to carry out a method according to the invention.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102014006692 A1 [0002]

Claims (9)

Method for calculating a soot amount Ms in a particulate filter (2), wherein in the calculation of a soot reduction M _SR in the particulate filter (2) is taken into account, and wherein in the calculation of the soot reduction M _SR a first particulate filter temperature T ₁ and an oxygen amount Mo are taken into account , Method according to Claim 1 , wherein in the calculation of the soot reduction M _SR an existing first soot loading M _{S1 of} the particulate filter (2) is taken into account. Method according to one of the preceding claims, wherein in the calculation of the soot reduction M _SR a second particulate filter temperature T ₂ (M _S1 ) is taken into account, and wherein T ₂ (M _S1 ) is dependent on the first soot load M _S1 . Method according to one of the preceding claims, wherein the duration t _{SR of} the soot reduction M _{SR is} taken into account in the calculation of the soot reduction M _SR . Method according to one of the preceding claims, wherein a first action for soot reduction in the particulate filter (2) is stopped when the soot reduction M _SR exceeds a threshold value for soot reduction. Method according to Claim 4 or 5 wherein the first action is aborted when the duration t _SR exceeds a duration limit. Method according to one of the preceding claims, wherein a second action for complete combustion of the amount of soot Ms in the particulate filter (2) is performed. Exhaust after-treatment system (1) comprising a controller (3) for a particulate filter (2) and a particulate filter (2), wherein the controller (3) is arranged for carrying out a method according to one of the preceding claims. A computer program product comprising a program which, when executed by a controller, causes the controller to perform a method according to the invention according to any one of Claims 1 to 7 perform.

Images